Five years after giving up his life of crime in the sewers, Montmorency is back in London. But his evil alter ego, Scarper has returned too, pulling him back into a dark world of crime.Montmorency's old friend and fellow government agent, Lord George Fox-Selwyn, fights to rescue him from disaster and risks calling in Montmorency's prison doctor, Robert Farcett, to help.However, when Montmorency turns up on a Scottish Island, he finds himself caught in another web of mystery.